Question

For each of the salts on the left, match the salts on the right that can...

For each of the salts on the left, match the salts on the right that can be compared directly, using Ksp values, to estimate solubilities.

(If more than one salt on the right can be directly compared, include all the relevant salts by writing your answer as a string of characters without punctuation, e.g, ABC.)

 1. lead iodide A. PbS 2. cobalt(II) carbonate B. Fe(OH)2 C. Cu(OH)2 D. BaSO4

Write the expression for K in terms of the solubility, s, for each salt, when dissolved in water.

Lead Iodide has the formula of PbI2 and Cobalt(II) Carbonate has the formula CoCO3

PbI2 -----> Pb(2+) + 2I-

Let the solubility of salt be s, then Ksp expression for PbI2 = s(2s)^2 = 4s^3

CoCO3 -----> Co(2+) + CO3(2-)

Ksp expression for CoCO3 = s^2

Hence lead iodide will map to B and C i.e. Fe(OH)2 and Cu(OH)2 all having Ksp of 4s^3

Hence cobalt (II) carbonate will map to A and D all having Ksp of s^2

b)

PbI2 -----> Pb(2+) + 2I-

Ksp = [Pb+2][I-]^2 = (s)(2s)^2 = 4s^3

CoCO3 -----> Co(2+) + CO3(2-)

Ksp = [Co(2+)][CO3(2-)] =s(s) = s^2